The invention relates to a composition comprising a mixture of synthetic thermoplastic compounds, particularly polyolefins and their copolymers which may also contain an elastomer having thermoplastic properties and further must contain a carbonaceous material and, if desired, conventional fillers. Compositions involving mixtures of the described kind are mainly used for sealing and protective purposes in the building and installation industry, for instance in the form of foils for making products watertight as sealing compounds for pipes and sealing profiles as well as protective coverings of containers, pipes, electric cables and many other articles. Apart from pure mixtures of synthetic materials on one hand and mixtures on the other hand on the base of tar a large number of other composition mixtures has been proposed which principally contain ethylene copolymerisates as the synthetic components and certain bitumens as carbonaceous materials and furthermore, if desired, conventional fillers. Advances in the art of the synthetic materials have made it possible to use more and more types of starting materials. However, the range of bituminous carbonaceous material has undergone a gradual narrowing since only bitumens of specific origin having specific properties could be used to obtain the desired properties in the final product.
In the U.S. Pat. No. 3,249,567 mixtures have been described of about 5 to 95% by weight aromatic asphalts obtained from petroleum and about 5 to 95% by weight of ethylene copolymerisates with a proportion of 10 to 40% by weight of alkyl ester relative to the weight of the copolymerisate. In testing specimens of these mixtures tensile strengths were obtained up to about 4.5 N/mm.sup.2 and elongations up to about 900%. The German accepted application 24 41 203 discloses shaped materials which essentially consist of ethylene copolymerisates and bitumen, the bitumen in this case being an extract- and/or precipitation bitumen which according to the German industrial norm DIN 1995 must exhibit a penetration at 25.degree. C. smaller than 10. Tests with these materials showed tensile strengths up to about 8 N/mm.sup.2 and elongations up to about 1100%.
From the German Pat. No. 1,948,526 ethylene copolymers containing bituminous sealing tapes have become known which consist of about 45 to 50% by weight of a mixture of polyethylene acrylic acid ester copolymerisate and a small fraction of bitumen, about 10 to 15% by weight of high pressure polyethylene and about 40% by weight of anthracite powder with a grain size up to 30.mu. and a proportion of non-combustible components of up to 30% by weight (relative to the anthracite powder fraction). Depending on the forming method (cast or extruded shapes) tensile strengths were obtained between 2 and 5 N/mm.sup.2 and elongations between 300 and 1000%.
Shaped bodies from the described mixtures, however, have the shortcoming of a heavily reduced tensile strength and elongation at a temperature of 50.degree. C. which has a most undesirable effect, for instance in case of the use of foils for roofing purposes. On the other hand, the range of raw materials is rather narrow in view of the bitumen and a scarcity of crude oil would have strong effects on the availability and price of the bitumen. The use, moreover, of crude oils of growing contents of sulfur and contaminations results in fluctuations of the quality of the bitumens which has an undesirable effect on the properties of the final composition.
It is, therefore, the problem of the present invention to broaden the range of raw materials for these mixtures of materials while maintaining the heretofore existing properties and, in addition, to improve the heat resistance of the materials.